Your parents would have to amend their return for that year and claim you as a dependent. It isn't something you can initiate. The exemption belongs to your parents if they qualify to take it.
If you are a dependent of someone (your parents), you cannot change the situation on his/her behalf. Ask your parents to amend their tax return. My recommendation is to work side by side with your CPA.
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I agree with the responses of both of the other attorneys. You cannot amend your parent's tax returns...they would need to do it.
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